test: Allow more error message variations in TestConnection.testTls
test: Allow more error message variations in TestConnection.testTls

This test often fails with an unexpected message

    couldn't read from connection: Peer sent fatal TLS alert: Unknown certificate

We don't care a lot about the precise TLS error message, and they tend
to change between OpenSSL versions, so be more liberal  about it.

cockpit-project/cockpit,cockpituous/cockpit,mvollmer/cockpit,deryni/cockpit,garrett/cockpit,moraleslazaro/cockpit,moraleslazaro/cockpit,deryni/cockpit,martinpitt/cockpit,martinpitt/cockpit,garrett/cockpit,garrett/cockpit,moraleslazaro/cockpit,cockpituous/cockpit,deryni/cockpit,deryni/cockpit,martinpitt/cockpit,moraleslazaro/cockpit,deryni/cockpit,moraleslazaro/cockpit,cockpituous/cockpit,moraleslazaro/cockpit,garrett/cockpit,cockpit-project/cockpit,cockpituous/cockpit,cockpituous/cockpit,moraleslazaro/cockpit,mvollmer/cockpit,mvollmer/cockpit,martinpitt/cockpit,deryni/cockpit,cockpit-project/cockpit,mvollmer/cockpit,cockpit-project/cockpit,cockpituous/cockpit,mvollmer/cockpit,deryni/cockpit,garrett/cockpit,cockpit-project/cockpit,martinpitt/cockpit